What's new in pg_clickhouse v0.10.0: Subqueries, TPC-H Speedups, C Driver, and Aggregates

pg_clickhouse v0.10.0 advances ClickHouse pushdown support for PostgreSQL analytic workloads, increasing full TPC-H query pushdown coverage from 12 to 16 of 22 queries and delivering major speedups for queries such as Q17, which fell from 32.7 seconds in an earlier version to 37 milliseconds. The release adds correlated subquery and safe IN/NOT IN pushdown, including safeguards that preserve PostgreSQL’s three-valued NULL semantics despite ClickHouse’s different default behavior, though this correlated-subquery support requires ClickHouse 25.8 or later. It also broadens support for functions, aggregates, partitionwise aggregation, date and time operations, JSON, arrays, window functions, and other SQL features, while making builtin function pushdown explicitly mapped to avoid semantic inconsistencies. Driver changes replace an earlier C++ client with a streaming C-based library, unify binary encoding across HTTP and binary paths, improve memory use, add compression and TLS settings, expand type support, and resolve concurrency and reliability issues. New query and procedure interfaces support arbitrary row-returning queries and effect-only commands against configured ClickHouse servers, while six TPC-H queries remain blocked mainly by join-tree deparsing limitations; future work also includes broader function coverage, UPDATE and DELETE support, and UNION pushdown.

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